Is extraembryonic endoderm a source of placental blood cells?

The fertilized egg of placental mammals establishes both the embryo and extraembryonic tissues which support the fetus during gestation. Four extraembryonic tissues, the allantois, chorion, yolk sac, and amnion, create the chorio-allantoic and chorio-vitelline (yolk sac) placentae and are conserved amongst all Placentalia. The allantois matures into the vascularized umbilical cord; the chorion forms the site of exchange between the fetus and its mother; the yolk sac, whose major components are extraembryonic mesoderm and extraembryonic endoderm, called “hypoblast” (humans/non-human primates) or “visceral endoderm” (mice), is a well-established site of primitive erythropoiesis; and the avascular amnion creates a shock-absorptive environment to protect the fetus.
Source: Experimental Hematology - Category: Hematology Authors: Source Type: research